Hypertension is 50%[unreadable] more common in blacks than whites in the U.S., and accounts for 20% of adult[unreadable] deaths among blacks. The causes of this increased risk are not well[unreadable] understood. Epidemiologic research has focused principally on black:white[unreadable] comparisons, where social and biological factors are confounded. In this[unreadable] competitive renewal application, the investigators request support to[unreadable] continue a large-scale research project on the evolution of hypertension[unreadable] risk across the course of the African diaspora. In this research project,[unreadable] known as The International Collaborative Study on Hypertension in Blacks[unreadable] (ICSHIB), the investigators have examined 18,000 individuals in Africa[unreadable] (Nigeria, Cameroon, Zimbabwe), the Caribbean (Barbados, St. Lucia, Jamaica)[unreadable] the UK (Manchester), and the U.S. (Maywood, IL). Using a standardized[unreadable] protocol, the gradient in risk from very low levels in rural Africa to in[unreadable] high levels in metropolitan Chicago have been characterized. The[unreadable] sociocultural determinants of these patterns have also been extensively[unreadable] documented.[unreadable] [unreadable] While population differences in risk status have been clearly documented,[unreadable] mechanistic studies will be required to understand the etiologic process.[unreadable] In the next phase the investigators propose to examine in further detail the[unreadable] role of the two most potent hypertensive risk factors, namely dietary sodium[unreadable] and obesity. Randomized trials will be carried out in Nigeria, Jamaica and[unreadable] Chicago to determine the relative sodium sensitivity of these populations[unreadable] and the factors which condition the blood pressure response. Studies of the[unreadable] renin-angiotensin system (RAS) and renal sodium handling will allow[unreadable] comparisons of the causal mechanisms. In addition, body composition will be[unreadable] studied in a large sample of each of these three populations to determine[unreadable] the role of body fat vs. lean body mass. Hormone status (i.e., insulin,[unreadable] leptin will be examined to define physiologic mechanisms, and physical[unreadable] activity will be measured by objective methods (using stable isotopes) to[unreadable] assess the role of sedentarism as a contributor to the hypertension risk[unreadable] experienced by the obese. Existing cohorts will be followed to determine[unreadable] hypertension sequelae and to examine the trajectory of blood pressure change[unreadable] with age.[unreadable] [unreadable] [unreadable] While previous hypertension research has often been largely confined to[unreadable] single cultural setting, much remains to be learned from broad contrasts[unreadable] across environments. The availability of new epidemiologic tools, including[unreadable] genetic markers, has created new opportunities in descriptive epidemiology.[unreadable] Multiple interactions are likely to occur among environmental and genetic[unreadable] risk factors; a broad range of environmental contrasts among genetically[unreadable] related populations creates a powerful research design to study these[unreadable] interactions. The African diaspora creates a unique opportunity for these[unreadable] cross-cultural studies.[unreadable]